HT45F23 datasheet(73/152 Pages) HOLTEK

73 / 152 page

The following diagram illustrates the waveforms associated with the 7+1 mode PWM operation. It is

important to note how the single PWM cycle is subdivided into 2 individual modulation cycles,

numbered 0 and 1 and how the AC value is related to the PWM value.

PWM Output Control

The PWM outputs are pin-shared with the I/O pins PC5 and PC6. To operate as a PWM output and not

as an I/O pin, the correct bits must be set in the BPCTL register. A high value must be written to the

PWM0EN or PWM1EN to select the corresponding PWM. A zero value must also be written to the

corresponding bit in the I/O port control register PCC.5 and PCC.6 to ensure that the corresponding

PWM output pin is setup as an output. After these two initial steps have been carried out, and of course

after the required PWM value has been written into the PWMn register, writing a high value to the

corresponding bit in the output data register PC.5 and PC.6 will enable the PWM data to appear on the

pin. Writing a zero value will disable the PWM output function and force the output low. In this way,

the Port data output registers can be used as an on/off control for the PWM function. Note that if the

BPCTL register has selected the PWM function, but a high value has been written to its corresponding

bit in the PCC control register to configure the pin as an input, then the pin can still function as a

normal input line, with pull-high resistor options.

PWM Programming Example

The following sample program shows how the PWM0 output is setup and controlled.

mov a,64h

;setup PWM value of decimal 100

mov pwm0,a

clr bpctl.7

;select the 7+1 PWM mode

set bpctl.5

;select PWM0

clr pcc.5

;setup pin PC5

set pc.5

;enable the PWM output

clr pc.5

; disable the PWM output pin,PC5 forced low

HT45F23/HT45F43

8-Bit Flash MCU with Op Amps & Comparators

Rev. 1.20

September 15, 2011

f S Y S / 2

P W M

[ P W M ] = 1 0 0

[ P W M ] = 1 0 1

P W M

[ P W M ] = 1 0 2

P W M

[ P W M ] = 1 0 3

P W M

P W M m o d u l a t i o n p e r i o d : 1 2 8 / f S Y S

5 0 / 1 2 8

5 1 / 1 2 8

5 2 / 1 2 8

5 0 / 1 2 8

5 1 / 1 2 8

5 0 / 1 2 8

5 1 / 1 2 8

5 2 / 1 2 8

M o d u l a t i o n c y c l e 0

P W M c y c l e : 2 5 6 / f S Y S

M o d u l a t i o n c y c l e 1

M o d u l a t i o n c y c l e 0

7+1 PWM Mode

P W M R e g i s t e r

( 7 + 1 ) M o d e

b 7

b 0

A C v a l u e

D C v a l u e

PWM Register for 7+1 Mode

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